Activation-induced spin modulation in Fe2O3-decorated CoP/cobalt molybdate hydrate for efficient alkaline hydrogen evolution

Fe 2 O 3 @CoP@CMOH/NF-A was constructed by ALD and electrochemical activation. • CoP acts as the key activation component, inducing Co-O-Mo cleavage and Co spin polarization. • Fe 2 O 3 loading triggers interfacial charge redistribution to further optimize Δ G H⁎ adsorption for HER. • Fe 2 O 3 @CoP@CMOH/NF-A requires only 23 mV for HER and 180 mV for OER at 10 mA cm −2 , and exhibits robust stability after 1000 h. Cobalt-based oxide catalysts are promising for alkaline water electrolysis owing to their natural abundance and structural stability, yet their hydrogen evolution reaction (HER) activity remains limited. Herein, a Fe 2 O 3 @CoP@cobalt molybdate hydrate/nickel foam (Fe 2 O 3 @CoP@CMOH/NF) catalyst was constructed through hydrothermal synthesis, vapor-phase phosphorization and atomic layer deposition (ALD), followed by in situ electrochemical activation to regulate the spin state of Co sites, yielding Fe 2 O 3 @CoP@CMOH/NF-A. Fe 2 O 3 @CoP@CMOH/NF-A catalyst exhibits excellent HER performance in 1.0 M KOH, requiring an overpotential of only 23 mV at 10 mA cm −2 and maintaining stability for over 1000 h. Experimental characterizations and density functional theory calculations reveal that CoP/CMOH interfacial interaction induces Co-O-Mo bond cleavage under an applied reductive potential, decreases the coordination number of Co sites, increases the population of unpaired electrons, and promotes Co 3d electron rearrangement, thereby enhancing Co-site spin polarization and optimizing hydrogen adsorption. Fe 2 O 3 further strengthens interfacial charge redistribution, increasing the effective magnetic moment from 1.98 μ B to 4.09 μ B and optimizing Δ G H⁎ from −0.98 to −0.46 eV. The catalyst also delivers excellent oxygen evolution reaction (OER) activity with an overpotential of 180 mV at 10 mA cm −2 and long stability for over 1000 h. As a bifunctional catalyst, it reaches 10 mA cm −2 at a cell voltage of 1.44 V for overall water splitting and maintains a low HER overpotential of 29 mV at 10 mA cm −2 for 1000 h in simulated seawater.